Photochemistry of microplastics-derived dissolved organic matter: Reactive species generation and organic pollutant degradation

Jie Zhang; Xianfeng Hou; Kena Zhang; Quanzhi Xiao; Jorge L Gardea-Torresdey; Xiaoxia Zhou; Bing Yan

doi:10.1016/j.watres.2024.122802

Photochemistry of microplastics-derived dissolved organic matter: Reactive species generation and organic pollutant degradation

Water Res. 2024 Nov 17:269:122802. doi: 10.1016/j.watres.2024.122802. Online ahead of print.

Authors

Jie Zhang¹, Xianfeng Hou², Kena Zhang¹, Quanzhi Xiao¹, Jorge L Gardea-Torresdey³, Xiaoxia Zhou⁴, Bing Yan¹

Affiliations

¹ Institute of Environmental Research at the Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, PR China.
² National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environmental Pollution Control and Management, Institute of Eco-Environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, PR China.
³ Department of Chemistry and Biochemistry, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, United States.
⁴ National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-Environmental Pollution Control and Management, Institute of Eco-Environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, PR China. Electronic address: xiaoxiazhou89@126.com.

PMID: 39579559
DOI: 10.1016/j.watres.2024.122802

Abstract

Dissolved organic matter (DOM) originating from microplastics (MPs-DOM) is increasingly recognized as a substantial component of aquatic DOM. The photochemistry of MPs-DOM, essential for understanding its environmental fate and impacts, remains largely unexplored. This study investigates the photochemical behaviors of MPs-DOM derived from two common plastics: polystyrene (PS) and polyvinyl chloride (PVC), which represent aromatic and aliphatic plastics, respectively. Spectral and high-resolution mass spectrometry analyses demonstrated that photoreactions preferentially targeted poly-aromatic compounds within the MPs-DOM, leading to degradation products that predominantly form N-aliphatic/lipid-like substances. This transformation is characterized by decreased aromaticity and unsaturation. Additionally, irradiation of MPs-DOM generated reactive species (RS), including triplet intermediates (³DOM*) and singlet oxygen (¹O₂), with apparent quantum yields of 0.06-0.16 % and 0.16-0.35 %, respectively-values considerably lower than those for conventional DOM (1.19-1.56 % for ³DOM* and 1.34-1.90 % for ¹O₂). Despite this, the RS generated from MPs-DOM significantly enhance the degradation of coexisting organic pollutants, such as antibiotic resistance genes (ARGs). The findings shed light on the photoinduced transformation of MPs-DOM and suggest that MPs-DOM functions as a natural photocatalyst, mediating redox reactions of pollutants in sunlit aquatic settings. This highlights its previously underestimated role in natural attenuation and aquatic photochemistry.

Keywords: Dissolved organic matter; FT-ICR-MS; Microplastics; Photochemistry; Reactive species.